Magnetron device and system



March 15, 1960 P. H. PETERS, JR

MAGNE'I'RON nsvxcs AND SYSTEM Filed April 1, 1958 Inventor Phi/lju H Peters, Jr.,

His Attorney.

United States Patent MAGNETRON DEVICE AND SYSTEM Philip H. Peters, Jr., Schenectady, N. assignor to General Electric Company, a corporation of New York Application April 1, 1958, Serial No. 725,576

Claims. (Cl. SIS-39.55)

The present invention relates to improved magnetron devices and systems and particularly to improved magnetron structures which are well adapted for voltage tunable operation.

In US. Patent 2,774,039, Peters et al., dated December 11, 1956, there is described and claimed a method and apparatus for tuning armagnetron system over a wide frequency range by varying the applied anode-cathode voltage. As outlined in that patent it has been found that the oscillating frequency of the magnetron system will vary directly with the direct current voltage applied to the anode-cathode circuit, provided the rate of increase of the high frequency voltage with respect to an increase in the direct current anode-cathode voltage is properly controlled. It is further stated that variation of the high frequency voltage with variation of the direct current anode-cathode voltage may be kept within the desired relationship if the anode circuit is heavily and uniformly loaded over the entire tuning range and, at the same time, a number of electrons in the interaction space is suitably limited. The present invention is directed particularly to an improved magnetron structure which is well suited for use in voltage tunable applications, particularly with respect to the stability of its operation at reasonably high power levels. It is also well suited for operation in rectangular output waveguide.

In accordance with the preferred embodiment of the present invention the high frequency output voltage is generated between a set of interdigital anode sections which are arranged in a cylindrical array having an angular extent equal to substantially less than 360 and preferably 180 or less. The space charge travels in an annular region defined by the array of anode elements and a non-emitting cathode for the angular extent of the anode sections, and by a continuous cylindrical anode surface and the non-emitting cathode member for the remainder of the circumference of the space charge region except for the region or regions at which the electrons are introduced to the interelectrode space. It will be apparent that with this arrangement the emitter is not subjected to any appreciable high frequency voltages and that it is therefore relatively free from the adverse effects of back heating. The magnetron is operated in a rectangular wave guide in a mode such that the anode sections con nected to one side of the wave guide are all of one polarity at a given time and with the amplitude of the high frequency voltage having a minimum value at each end of the array of anode sections and a maximum value in the middle of the array. Such a distribution corresponds closely to the electric field distribution desired across the width of the rectangular wave guide operating in the TE mode. The space charge in the device is gradually bunched as it enters the high frequency voltage generating region of the interdigital anode sections and likewise leaves the high frequency field in a region of gradually decreasing amplitude. stability of operation. Also any electrons which tend to make more than one excursion around the interelectrode This tends to provide maximum nate metal terminal members and ceramic spacer mem 2,928,987 Patented Mar. 15, 1960- space bear little evidence of their previous excursion past the high frequency region of the anode and the phasing problem of the electrons with respect to the anode sections is minimized.

It is therefore an important object of the present invention to provide an improved magnetronstructure capable of stable operation over a substantial frequency range in voltage tunable applications and at substantial power output levels.

Further objects and advantages of my invention will become apparent as the following description proceeds, reference being had to the accompanying drawing and its scope will be pointed out in the appended claims. 7 In the drawing Figure 1 is a perspective view of a magnetron system including a magnetron device and rectangular output wave guide in accordance with my invention;

Figure 2 is a plan view partially broken away illustrating the details of construction of the discharge device shown in Figure 1;

Figure 3 is a sectional View taken'along the line 33 of Figure 2;

Figure 4 is an elevational view illustrating the construction of the emitter used in the device shown in Figures 2 and 3;

Figure 5 is a plan view, partially broken away, of a modified magnetron device embodying my invention, and

Figure 6 is an elevational view partially in section taken along line 6-6 of Figure 5.

In Figure 1 my invention is illustrated in a magnetron system including an improved magnetron device designated generally by the numeral 10 supported at the thin-.

ner end 11 of a tapered rectangular output wave guide 12. As shown in Figures 2 and 3 the magnetron device 10 includes a vacuum tight envelope made up of alterbers. Specifically, the envelope includes a pair of end disk-like terminals 13 and 14 and a pair of annular anode' terminals 15 and 16. Three annular ceramic insulating members 17, 18 and 19 are interposed, respectively, be-

tween terminals 13 and 15, 15 and 16, and 16 and 14.'

As will be readily appreciated, the ceramic spacers and metal terminal members are bonded together by vacuum tight seals which may be formed in accordance with any one of a. number of ceramic-to-metal sealing processes well known in the art.

In the illustrated embodiment the active or high frequency portion of the anode structure is made up of a plurality of anode sections 20 and 21 arranged in a cylindrical array with alternate sectionssupported respective- 15 and 16.v The array of ly from the anode terminals activeanode sections extends over'180f'or less and in the embodiment illustrated has an' angular extentof approximately symmetrically located with respect to the center of the wave guide .12 and facing in the direction of propagation of the electromagnetic output energy from the device. The anode structure cylindrical conducting member the remainder of the 360 faces of the anode sections, terminals 15 and 16 so that voltages the entire anode nected.

An annular space charge region or interaction space is defined by the anode structure just described and acooperating non-emitting cathode member having 'the' form of a hollow cylinder which may be to advantage be made on thesame radius as the and supported from the anode with respect to direct current structure is conductively conintegrally with the end terminal 14 and supported therewithin the anode structure;- member 23 is provided with; thereof in .an angular position? opposite the array of anode sections 20, 21, within which from in concentric relation The non-emitting cathode an opening 24in the wall is completed by a solid 22 extending throughout" is supported an indirectly heated structure. The emitting cathode may be formed of sheet nickel having the form of a small section of a cylindrical surface having the same radius as that of the non-emitting cathode and supported from the non-emitting cathode by a plurality of tab supports 26. On the outer surface of the cathode 25 is a coating of good electron emitting material such as a conventional alkaline earth oxide coating. The cathode is heated by a heater element 27 secured to the opposite side and including supply conductors 28 connected with externally accessible lead-in conductors 29 and 30 extending through openings 31 and 32 in the terminal 14 and suitably sealed therethrough in insulated relation therewith by insulating disks 33. If the metal parts of the discharge device, particularly the envelope parts are of copper or similar metal, a continuous getter material may be provided within the device. As illustrated a sheet of titanium 34 is secured to an inner wall of the non-emitting cathode portion to provide continuous gas absorbing action during the operating life of the device.

The discharge device is supported in the rectangular wave guide with the anode terminals 15 and 16, respectively, connected to the opposite sidewalls of the guide. As illustrated, the guide is suitably apertured and recessed to receive the anode terminal 16 and provide for the insertion of the device through the upper wall of the guide. The device is secured in position by an annular ring 35 screwed into the wall of the guide and engaging the terminal 15.

In one magnetron system of the type described the discharge device included 36 anode sections distributed over an angular extent of 90 on a. radius of approximately .7 inch. The non-emitting cathode surface had a radius of approximately .65 inch and the vane height was approximately .5 inch. The direct current anode-cathode voltage was about 2000 volts for a center frequency of 3000 megacycles and a magnetic field strength in an axial direction of about 1500 gauss. Voltage tuning over a ten percent tuning range was observed at a tuning rate of approximately 1.5 megacycles per volt change in the anode-cathode voltage.

As apparentfrom the foregoing detailed description the present invention provides a magnetron device and system suitable for voltage tunable operation and particularly well suited for operation in a rectangular wave guide. The construction affords a source of space charge which is relatively free from the efiects of back heating and therefore renders the operation stable. Also, the distribution of the anode sections with respect to the wave guide cross section is compatible with operation of the output guide in the TE mode. The device is compact, being much shorter in an axial direction than magnetron devices using axial or endwise injection to protect, the emitter from the effects of back heating. This makes possible the use of a smaller magnet structure for producing the desired axial magnetic field strength. i

In Figures and 6 I have illustrated a modification of my invention which is essentially the same as that already described in connection with the preceding figures except for the source of electrons. In the modification of Figures 5 and 6 two directly heated thoriated tungsten spiral emitters 36 and 37 are provided in the space between the nonemitting cathode 23 and the anode at spaced angular positions generally opposite to the location of the anode segments. These spirals are supported from pins 38 brazed to the opposite end terminals 13 and 14 of the device. In this modification the nonemitting cathode 23 is made continuous and is provided with semicircular recesses 39 located opposite to similarly shaped recesses 40 formed in the continuous portion 22 of the anode surface. These recesses form cylindrical surfaces around each emitter. The geometry corresponds to a split anode magnetron with one anode 4 connected to the emitter. This structure may be designed to have the same cutoif voltage as the main interelectrode space.

This construction oifers advantages similar to those of the previous modification and makes possible the use of directly heated cathodes. The spaced cathodes also provide for the introduction of space charge at annularly displaced positions which facilitates the production of the desired space charge density and distribution.

While I have described a particular embodiment of my invention it will be apparent to those skilled in the art that changes and modifications may be made without departing from-my invention in its broader aspects and I aim, therefore, in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A magnetron device including an envelope, a substantially cylindrical non'emit-ting cathode electrode positioned within said envelope, an anode structure supported within said envelope and surrounding said non-emitting cathode to define therewith a substantially annular and angularly continuous space charge region, said anode structure including a substantially continuous cylindrically shaped conducting surface having an angular extent of at least and a plurality of anode sections between the ends of said cylindrical conducting member, mutually insulated terminals supported from said envelope with alternate ones of said anode sections connected to a different one of said terminals, a recess in said non-emitting cathode in said angular region opposite the continuous conducting portion of said anode structure and a cathode supported within said recess.

'2. A magnetron device including an envelope, a substantially cylindrical non-emitting cathode electrode positioned within said envelope and surrounding said nonemitting cathode to define therewith a substantially annular and angularly continuous space charge region, said anode structure including a substantially continuous cylindrical conducting surface having an angular extent of at least 180 and a plurality of anode sections between the ends of said cylindrical conducting member, mutually insulated terminal means supported from said envelope with alternate ones of said anode sections connected to a different one of said terminals, and means for introducing electrons into said annular space charge region.

3. A magnetron device comprising an anode structure including a pair of generally annular terminal members, a substantially cylindrically shaped member supported from said terminal members and having an angular extent of at least 180, a plurality of anode sections positioned in side-by-side and angularly spaced relation throughout the remainder of the circumference of said terminal members with alternate sections connected to and supported from a difierent one of said terminal members, a generally cylindrical non-emitting cathode supported within said anode structure to provide a substantially annular and angularly continuous space charge region between said anode structure and said cathode and means for supplying electrons to said annular space charge region at an angular position remote from said anode sections.

4. A magnetron device comprising a substantially cylindrical envelope structure including a conducting end wall and a pair of generally annular terminals sealed in the side wall thereof in mutually spaced and insulated relation, a generally cylindrical non-emitting cathode supported from said conducting end wall and an anode structure surrounding said non-emitting cathode in spaced relation therewith to provide therebetween an annular and angularly continuous space charge region, said anode structure including a substantially continuous conducting member of cylindrical shape supported from said anode terminals and having an angular extent greater than 180, a plurality of anode sections relatively narrow circumferentially supported in spaced relation between the ends of said continuous conducting member with alternate sections connected to a difierent one of said terminals, said non-emitting cathode having a recess therein in the region radially opposite said continuous conducting member, and a cathode positioned in said recess for introduoing electrons into said space charge region.

5. In combination a rectangular wave guide having a tapered section gradually increasing in height and connected at the smaller end thereof with a section of wave guide of uniform height, a generally cylindrical magnetron device having a pair of axially spaced anode terminals coupled to opposite walls of said section of wave guide of uniform height, a substantially cylindrically shaped anode member supported from said terminal members and having an angular extent of at least 180, said member being symmetrically positioned with respect to the longitudinal axis of said wave guide and positioned 20 toward the end of said wave guide section of uniform height remote from said tapered section of wave guide, a plurality of anode sections positioned in side-by-side and angularly spaced relation throughout the remainder of the circumference of said terminal members with alternate sections connected to and supported from a different one of said terminal members, a generally cylindrically non-emitting cathode supported within said anode structure to provide a substantially annular space charge region between said anode structure and said non-emitting cathode and means for supplying electrons to said annular space charge region at an angular position remote from said anode sections.

References Cited in the file of this patent UNITED STATES PATENTS 2,582,185 Willshaw Jan. 8, 1952 2,760,111 Kumpfer Aug. 21, 1956 FOREIGN PATENTS 678,370 Great Britain Sept. 3, 1952 

